Population research at Johns Hopkins has benefited greatly from the facilities provided by the Hopkins Population Center. The list of publications and working papers submitted with this application document a sustained high level of research output in demography and reproductive biology. The Population Center provides a variety of services and facilities which stimulate and advance research activity, bringing together investigators interested in population by providing a first class library and documents center, by supporting computer facilities and software development, by the availability of a central group for consultation of reearch design and analysis and by encouraging inter-departmental collaboration in reproductive biology through support of the Reproductive Biology Council and the Core EM laboratory. Funds are requested for a renewal of this support, specifically for a Directorate to attend to overall coordination; a Population Information Unit with capacity for sophisticated information retrieval; and Data Processing Unit which provides remote entry terminals, data management services, software development and guidance in operating in the University's complex computational environment; the Core EML laboratory, and the Mathematical and Statistical Services Unit. The Hopkins Center is unique in that it contains two parallel structures: a demographic division and a reproductive biology division. There is frequent interaction between these divisions but essentially each one is self contained with its own network of investigators. All of the core facilities except the EM laboratory are utilized by both divisions. Two developmental programs are proposed. One is in the area of cell interaction and function in vitro. This program calls for recruiting a junior member of the Reproductive Biology faculty who would establish a cell culture laboratory and whose area of specialization would be cell-cell interaction, mesenchymal-stromal- epithelial cell interaction or the role of the tissue-specific extracellular matrix in the function of cultural cells from reproductive tissue. A second developmental program proposes to develop clinico-epidemiological studies of reproductive health and contraception with special reliance on urinary hormonal assays.